The present invention is directed to an improved tool grinding machine and, more particularly, to a tool grinding machine that incorporates components which provides for monitoring the grinding rate on the tool so that variations in hardness and thickness of the tool may be readily compensated for during the grinding procedure.
The technological requirements of many present day systems require that the components of the system be machined to very precise specifications. In order to provide this precise machining the machine such as a lathe, boring mill, or other component machining mechanisms requires the use of special cutting tools. For example, single point diamond and tungsten carbide cutting tools have been used successfully in highly precision machines for accurate and precise machine operations. More particularly, single point diamond tools with a radiused cutting edge are readily utilized for machining laser beam reflecting mirrors envisioned for use in the laser fusion program. Such cutting tools require a roundness accuracy of less than 30 microinches and a radius tolerance of no more than about 0.001 inch for cutting the mirrors to within the predetermined finished surface tolerances. Single point cutting tools including those made of diamond and other materials, such as tungsten carbide, which are ground to precise specifications such as described above, are of limited availability and are relatively expensive.
To grind a single point diamond tool with a desired point radius and within the roundness tolerances as previously practiced, the tool was mounted in a holder affixed to an arm capable of swinging the tool about an axis parallel to the face of the grinding wheel for forming an arc to grind a point radius on a single point tool. The point radius may be readily changed by relocating the pivot point of the arm.
The major problem associated with the precision grinding of single point diamond tools as previously practiced is due to the fact that the apparent hardness of the diamond varies along the edge being ground as caused by the orientation of the diamond crystals so as to introduce a considerable variance in the grinding rate on the cutting edge. In other words, the "softer" surfaces may be ground at a considerably faster rate than the "harder" surface areas. Another variable in diamond tools which introduces some difficulty in providing a precision ground tool is due to irregularities in thickness of the cutting tool caused by variations in the size and shape of diamonds used for cutting tools. These variations in thickness have a considerable affect upon the grinding rate since the thinner cross sections are usually ground at a faster grinding rate than the thicker sections in sections of similar hardness.